CN117730210A

CN117730210A - Sliding structure

Info

Publication number: CN117730210A
Application number: CN202280037341.9A
Authority: CN
Inventors: 堀场夏峰; 上坂裕之
Original assignee: National University Corp Donghai National University; Sanyou Special Precision Co ltd
Current assignee: National University Corp Donghai National University; Sanyou Special Precision Co ltd
Priority date: 2021-08-27
Filing date: 2022-08-23
Publication date: 2024-03-19
Also published as: WO2023027055A1; JPWO2023027055A1

Abstract

The present invention provides a sliding structure which has a simple structure and has excellent water lubrication sliding characteristics. The sliding structure (1) is provided with a first sliding member (10) and a second sliding member (20) each having a sliding surface, wherein the sliding surfaces are in contact with each other via a water layer (30), and the first sliding member (10) and the second sliding member (20) slide relative to each other, wherein the first sliding member (10) and the second sliding member (20) each have a base material (11, 21) and a hard layer (12, 22) formed on the surface of the base material (11, 21) as the sliding surface, and wherein the hard layer (12, 22) of the first sliding member (10) and the second sliding member (20) has a nano silica layer (13, 23) on which nano silica particles are supported. According to this structure, the surfaces of the nano silica layers (13, 23) are covered with the water layer (30), and the first and second sliding members (10, 20) slide relative to each other with low friction by applying an appropriate sliding speed and load, thereby exhibiting water-lubricated sliding characteristics.

Description

Sliding structure

Technical Field

The invention relates to a sliding structure, in particular to a sliding structure based on water lubrication.

Background

Conventionally, mechanical seals using ceramics lubricated with water have been used for bearings of underwater pumps and the like (for example, refer to patent document 1). Patent document 1 discloses an invention in which a silane coupling agent is added to a pin plate test of a ceramic material to form a film of a siloxane bond on the ceramic surface, thereby exhibiting water lubrication characteristics.

In addition, a technique has been proposed in which a hard carbon film such as diamond-like carbon is used as a coating material for sliding members and the like (for example, refer to patent document 2).

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 01-290577

Patent document 2: japanese patent No. 6095090

Disclosure of Invention

However, the conventional technology of patent document 1 has a problem that ceramics used are difficult to process and have high cost. In addition, in the method of the prior art, an appropriate amount of aqueous solution must be added to the friction surface, and therefore, many problems remain in practical use.

On the other hand, the conventional technique of patent document 2 has the following problems: the average height of the droplets in the first sliding member becomes smaller than the amount of elastic deformation generated in the first sliding member due to the load from the second sliding member when the first sliding member and the second sliding member slide, and before the first sliding member is subjected to the running-in process, the first sliding member and the second sliding member need to be subjected to running-in process in the absence of the liquid, which requires production costs.

The present invention has been made in view of the above-described problems, and an object thereof is to provide a sliding structure exhibiting excellent water-lubricated sliding characteristics with a simple configuration.

The sliding structure of the present invention is a sliding structure comprising a first sliding member and a second sliding member each having a sliding surface, wherein the sliding surfaces are in contact with each other via a water layer, whereby the first sliding member and the second sliding member slide relative to each other, wherein the first sliding member and the second sliding member each have a base material and a hard layer as a sliding surface on a surface of the base material, and wherein the hard layer of at least one of the first sliding member and the second sliding member has a nanosilica layer on which nanosilica particles are supported.

In the sliding structure according to the present invention, the hard layer of at least one of the hard layers has hydroxyl groups on the surface.

In the sliding structure according to the present invention, the nanosilica layer is supported on the hard layer in association with a covalent bond between an activated hydroxyl group of the hard layer and a hydroxyl group of the nanosilica particle.

In the sliding structure according to the present invention, each of the hard layers of both the first and second sliding members includes the nano silica layer.

In the sliding structure of the present invention, the hardness of each hard layer is 1000Hv or more.

In the sliding structure according to the present invention, the hard layer of at least one of the first and second sliding members is made of diamond-like carbon formed on the surface of the base material.

In the sliding structure according to the present invention, the diamond-like carbon contains silicon.

In the sliding structure according to the present invention, the hard layer of at least one of the first and second sliding members is a part of the base material.

In the sliding structure according to the present invention, the base material constituting the hard layer is made of ceramic.

In the sliding structure according to the present invention, each of the hard layers of both the first and second sliding members is a part of each of the base materials, and each of the base materials constituting each of the hard layers is made of ceramic.

According to the sliding structure of the present invention, the surface of the nano silica layer is covered with the water layer, and the first and second sliding members slide against each other with low friction by loading an appropriate sliding speed and load, thereby exhibiting water lubrication characteristics. This provides a sliding structure having a simple structure and excellent water-lubricated sliding characteristics.

Drawings

Fig. 1 is a sectional view schematically showing a sliding structure according to a first embodiment of the present invention.

Fig. 2 is a sectional view schematically showing a sliding structure of a second embodiment of the present invention.

Fig. 3 is a sectional view schematically showing a sliding structure according to a third embodiment of the present invention.

Fig. 4 is a sectional view schematically showing a sliding structure according to a fourth embodiment of the present invention.

Fig. 5 is a perspective view showing a pair of test pieces as the subjects of the frictional wear test.

Fig. 6 is a cross-sectional view showing a frictional wear testing machine and a test jig used in the frictional wear test.

FIG. 7 is a graph showing the difference in oxygen counts before and after the loading of the silica nanoparticles in each test piece.

Fig. 8 is a graph showing the results of the frictional wear test of example 1 and comparative example 1.

Fig. 9 is a graph showing the results of the frictional wear test of example 2 and comparative example 2.

Fig. 10 is a graph showing the results of the frictional wear test of example 3.

Fig. 11 is a graph showing the results of the frictional wear test of examples 4 and 5.

Fig. 12 is a graph showing the results of the frictional wear test of example 6.

Fig. 13 is a graph showing the results of the frictional wear test of example 7 and comparative example 3.

Fig. 14 is a graph showing the results of the frictional wear test of example 8.

Fig. 15 is a graph showing the results of the frictional wear test of example 9.

Detailed Description

Hereinafter, embodiments of the sliding structure according to the present invention will be described with reference to the drawings.

< first embodiment >, first embodiment

First, the structure of a sliding structure 1 according to a first embodiment of the present invention will be described with reference to fig. 1. Fig. 1 is a sectional view schematically showing a sliding structure 1 according to a first embodiment of the present invention.

The sliding structure 1 includes first and second sliding members 10 and 20 each having a sliding surface, and the sliding surfaces are in contact with each other via a water layer 30, whereby the first and second sliding members 10 and 20 slide relative to each other.

The first and second sliding members 10 and 20 each have a base material 11 and 21, and hard layers 12 and 22 as sliding surfaces formed on the surfaces of the base materials 11 and 21.

The base materials 11 and 21 are each made of steel, and the surfaces thereof are arranged to face each other in parallel. For example, the base materials 11 and 21 may be formed by processing SUS440C into a predetermined shape and quenching the SUS to a quenching hardness HRC 58. Further, the surfaces of the base materials 11 and 21 facing each other are polished to have a surface roughness ra0.01, for example.

The hard layers 12 and 22 are layers formed on the surfaces of the base materials 11 and 21 facing each other. More specifically, each hard layer 12, 22 is formed by applying a silicon-containing diamond-like carbon (hereinafter referred to as si—dlc) coating.

The hard layers 12 and 22 of both the first and second sliding members 10 and 20 each include a nanosilica layer 13 and 23 on which nanosilica particles are supported.

Specifically, the nano silica layers 13 and 23 are formed by first subjecting the hard layers 12 and 22 to atmospheric pressure plasma treatment with Ar gas to activate surface hydroxyl groups, and in this state, water-dispersible colloidal silica is applied to the surfaces of the hard layers 12 and 22 to adhere the surface hydroxyl groups of the water-dispersible nano silica particles. Then, the hydroxyl groups on the surfaces of the hard layers 12 and 22 are dehydrated and condensed with the hydroxyl groups on the surfaces of the nano silica particles at the time of drying, and then covalently bonded, whereby the nano silica layers 13 and 23 carrying the nano silica particles are formed on the hard layers 12 and 22. The covalent bonding by dehydration condensation of the hydroxyl groups on the surfaces of the hard layers 12 and 22 and the hydroxyl groups on the surfaces of the nano silica particles is a necessary condition for preventing the nano silica particles from falling off during the rubbing in water, but the covalent bonding is not necessarily performed reliably in the initial stage. Before the first and second sliding members 10 and 20 are used, it is sufficient to ensure that the nano silica particles are in a state of covering the hard layers 12 and 22 without falling off. The atmospheric pressure plasma treatment is not limited to Ar gas, and a gas capable of activating the surface hydroxyl groups, such as oxygen and nitrogen, may be used. Further, as a method for activating the surface hydroxyl groups, a method of irradiation with ultraviolet rays, electron beams, gamma rays, or the like may be used in addition to the atmospheric pressure plasma treatment.

The water layer 30 is a water layer interposed between the nano-silica layers 13 and 23 and covering the surfaces of the nano-silica layers 13 and 23. If the nano-silica layers 13, 23 overlap each other, the water layer 30 is interposed therebetween. Then, by loading an appropriate sliding speed and load, the water lubrication characteristic is exhibited.

< second embodiment >

Next, the structure of the sliding structure 2 according to the second embodiment of the present invention will be described with reference to fig. 2. Fig. 2 is a sectional view schematically showing a sliding structure 2 according to a second embodiment of the present invention. Note that the same reference numerals are given to the same components as those of the first embodiment, and detailed description thereof is omitted (the same applies to other embodiments).

In the first embodiment, the nano silica layers 13 and 23 are provided on the hard layers 12 and 22 of both the first and second sliding members 10 and 20, respectively. In the present embodiment, as shown in fig. 2, the nano silica layer 23 is formed only on the hard layer 22 of the second sliding member 20, and the nano silica layer 13 is not formed on the hard layer 12 of the first sliding member 10.

Therefore, in the present embodiment, the aqueous layer 30 is formed between the surface of the hard layer 12 of the first sliding member 10 and the nano silica layer 23 of the second sliding member 20.

< third embodiment >

Next, the structure of the sliding structure 3 according to the third embodiment of the present invention will be described with reference to fig. 3. Fig. 3 is a sectional view schematically showing a sliding structure 3 according to a third embodiment of the present invention.

In the present embodiment, the base material 11 of the first sliding member 10 is made of the same steel material (e.g., SUS 440C) as in the first embodiment described above. The base material 21 of the second sliding member 20 is made of ceramic (for example, silicon nitride, silicon carbide, or the like), and the base material 21 itself also serves as the hard layer 22 in the first embodiment. The nano silica layer 23 is formed only on the surface of the base material 21 of the second sliding member 20, and the nano silica layer 13 is not formed on the hard layer 12 of the first sliding member 10.

< fourth embodiment >, a third embodiment

Next, the structure of the sliding structure 4 according to the fourth embodiment of the present invention will be described with reference to fig. 4. Fig. 4 is a sectional view schematically showing a sliding structure 4 according to a fourth embodiment of the present invention.

In the present embodiment, the base material 11 of the first sliding member 10 is made of ceramic (for example, silicon nitride, silicon carbide, or the like), and the base material 11 itself also serves as the hard layer 12 in the first embodiment. In addition, a nano silica layer 13 is formed on the surface of the base material 11 of the first sliding member 10. Similarly, the base material 21 of the second sliding member 20 is made of ceramic (for example, silicon nitride, silicon carbide, or the like), and the base material 21 itself also serves as the hard layer 22 in the first embodiment. In addition, a nano silica layer 23 is formed on the surface of the base material 21 of the second sliding member 20.

Therefore, in the present embodiment, the aqueous layer 30 is formed between the nano silica layer 23 of the first sliding member 10 and the nano silica layer 23 of the second sliding member 20.

Summary of the first to fourth embodiments

The sliding structures 1 to 4 according to the first to fourth embodiments of the present invention are sliding structures including first and second sliding members 10 and 20 each having a sliding surface, the sliding surfaces being in contact with each other via a water layer 30, whereby the first and second sliding members 10 and 20 slide relative to each other, the first and second sliding members 10 and 20 each having a base material 11 and 21 and a hard layer 12 and 22 formed on the surface of the base material 11 and 21 as a sliding surface, and the hard layer 12 or 22 of at least one of the first and second sliding members 10 and 20 having a nanosilica layer 13 or 23 on which nanosilica particles are supported.

According to this configuration, the surface of the nano silica layer 13 or 23 is covered with the water layer 30, and the first and second sliding members 10 and 20 slide against each other with low friction by applying an appropriate sliding speed and load, thereby exhibiting water-lubricated sliding characteristics. This provides a sliding structure having excellent water lubrication characteristics with a simple structure.

In addition, the surface of the hard layer 12 or 22 provided with the nano-silica layer 13 or 23 has hydroxyl groups. The nanosilica layer 13 or 23 is supported on the hard layer 12 or 22 in association with a covalent bond between the activated hydroxyl group of the hard layer 12 or 22 and the hydroxyl group of the nanosilica particle.

According to this configuration, the nano silica layer 13 or 23 carrying the nano silica particles can improve the water-lubricated sliding characteristics.

In the sliding structure 1 according to the first embodiment, the hard layers 12 and 22 of both the first and second sliding members 10 and 20 are provided with the nano silica layers 13 and 23, respectively.

According to this configuration, by providing the nano silica layers 13 and 23 in the first and second sliding members 10 and 20, respectively, the water-lubricated sliding characteristics can be further improved.

The hardness of the hard layers 12, 22 is 1000Hv or more.

According to this structure, the hard layers 12 and 22 having a vickers hardness of 1000Hv or more can realize a low-friction sliding characteristic.

In the sliding structures 1 and 2 according to the first and second embodiments, the hard layer 12 or 22 of at least one of the first and second sliding members 10 and 20 is made of diamond-like carbon formed on the surface of the base material 11 or 21. In particular, diamond-like carbon may also contain silicon.

According to this structure, the hard layer 12 or 22 is made of diamond-like carbon formed on the surface of the base material 11 or 21, so that the sliding property with low friction can be reliably achieved.

In the sliding structure 3 according to the third embodiment, the hard layer 12 or 22 of at least one of the first and second sliding members 10, 20 is a part of the base material 11 or 21. In particular, the base material 11 or 21 constituting the hard layer 12 or 22 is made of ceramic.

According to this structure, when a material having a sufficient hardness (for example, a ceramic such as silicon nitride or silicon carbide) is used as the base material 11 or 21, the base material can also serve as the hard layer 12 or 22, and therefore, excellent water lubrication characteristics can be further exhibited with a simple structure.

In the sliding structure 4 according to the fourth embodiment, the hard layers 12 and 22 of both the first and second sliding members 10 and 20 are part of the base materials 11 and 21, respectively, and the base materials 11 and 21 constituting the hard layers 12 and 22 are made of ceramics.

According to this structure, when a material having a sufficient hardness (for example, a ceramic such as silicon nitride or silicon carbide) is used as the base material 11 or 21, the base material can also serve as the hard layers 12 or 22, and therefore, excellent water lubrication characteristics can be further exhibited with a simple structure.

Examples

Hereinafter, examples of the above embodiments will be described. First, a brief description will be given of a frictional wear test commonly used in each example, with reference to fig. 5 to 7. Fig. 5 is a perspective view showing a pair of test pieces as the subjects of the frictional wear test. Fig. 6 shows a cross-sectional structure of the frictional wear testing machine 100 and the test jig 200 used in the frictional wear test. FIG. 7 is a graph showing the difference in oxygen counts before and after the loading of silica nanoparticles in each test piece.

In each example, as the first slide member 10 and the second slide member 20 constituting the slide structures 1 to 4 of the first to fourth embodiments, as shown in fig. 5, a pair of test pieces, namely, an annular test piece having an annular shape and a disc-shaped test piece having a disc shape, was used to conduct the annular disc test. The annular test piece as the first slide member 10 was annular with an outer diameter of 16mm and an inner diameter of 11.4mm, and had a thickness of 7mm. The disk-shaped test piece as the second slide member 20 was square in shape with a side length of 20mm and a thickness of 4mm.

In the frictional wear test of each example, a frictional wear tester (model EFM-3-H) manufactured by Kagaku Co., ltd. Was used. As shown in fig. 6, the frictional wear testing machine 100 includes a load mechanism 101 provided at an upper part of the device and applying a downward load to a pair of test pieces, and a rotation mechanism 102 provided at a lower part of the device and rotating one of the pair of test pieces.

In addition, the test jig 200 is used as a jig for mounting an annular test piece (first slide member 10) and a disk-shaped test piece (second slide member 20) on the frictional wear testing machine 100. The test fixture 200 includes an upper fixture 201 for mounting the ring-shaped test piece on the load mechanism 101, and a lower fixture 202 for mounting the disk-shaped test piece on the rotation mechanism 102. The upper clamp 201 is configured to be variable in posture angle with respect to the load mechanism 101 via the steel ball 201a, and the annular test piece is always aligned with the disk-shaped test piece. The lower clamp 202 has a concave shape on the upper surface, and can store water. The surface of the annular test piece and the surface of the disk-shaped test piece, which are opposed to each other and overlap each other, are submerged under the water surface, and water is supplied into the concave portion of the upper surface of the lower clamp 202.

In each example, the difference in oxygen count values before and after the loading of the silica nanoparticles was obtained by counting the oxygen amount of each test piece using a scanning electron microscope and an energy-dispersive X-ray detector (see fig. 7). The amount of oxygen present in the nanosilica layer but not in the hard layer is counted, whereby the amount of nanosilica particles supported can be estimated. Since the count value of the oxygen amount varies with the amount of the surface hydroxyl groups of the hard layer, it was found that the amount of the nano silica particles supported by the above method was observed.

Example 1

The annular test piece (first sliding member 10) of example 1 was prepared by setting the hard layer 12 as a Si-DLC coating having a Si content of 25%, and setting the nanosilica layer 13 as a nanosilica particle size 9 nm. Similarly, the disk-shaped test piece (second sliding member 20) of example 1 was a Si-DLC coating having a hard layer 22 with a Si content of 25%, and a nanosilica layer 23 was supported with a nanosilica particle diameter of 9 nm.

Test conditions: the sliding speed was 12[ mm/s ], and the test pieces were used as ring-shaped test pieces (phi 16 x phi 11.4 x 7[ mm ] (which means that the outer diameter was 16mm, the inner diameter was 11.4mm, the thickness was 7mm, and the same was true in other examples, etc.), and as disk-shaped test pieces, 20 x 4[ mm ], and were loaded under a vertical load of 50N for 60 seconds, and then, the test pieces were loaded for 30 seconds every 200N, and were standby for 60 seconds under 4800N, and then, the test pieces were terminated.

Comparative example 1

For comparison with example 1, the frictional wear test of comparative example 1 was performed under the same test conditions. The annular test piece of comparative example 1 was a Si-DLC coating having a Si content of 25% in the hard layer 12, and no nano silica was supported. Similarly, the disk-shaped test piece of comparative example 1 was a Si-DLC coating having a Si content of 25 in the hard layer 22, and no nano silica was supported. The test conditions were the same as in example 1.

(test results of example 1 and comparative example 1)

Fig. 8 is a graph showing the results of the frictional wear test of example 1 and comparative example 1. In the graph of fig. 8, the vertical axis represents the friction coefficient, and the horizontal axis represents the interfacial contact pressure (the same applies to fig. 9 to 12). As shown in fig. 8, the contact pressure between the surfaces during sliding was at least 48.5MPa in example 1 and 24MPa in comparative example 1. Here, the interfacial contact pressure (unit MPa) is a value obtained by dividing the vertical load (unit N) by the contact area (about 100 square millimeters) between the annular test piece and the disk-shaped test piece. In addition, the coefficient of friction at the time of low friction sliding in example 1 was smaller than that in comparative example 1, and the low friction was exhibited. From the above results, it was shown that the nano silica layer is important for improvement of water-lubricated sliding. In the present specification, low-friction sliding means sliding with a friction coefficient of 0.1 or less.

Example 2

The annular test piece (first sliding member 10) of example 2 was prepared by setting the hard layer 12 as a DLC coating (hydrogen-containing amorphous carbon, hereinafter referred to as "a-C: H") having a Si content of 0%, and setting the nanosilica layer 13 as a nanosilica particle size 9 nm. Similarly, the disk-shaped test piece (second sliding member 20) of example 2 was prepared by setting the hard layer 22 as a DLC coating layer (a-C: H) having a Si content of 0% and setting the nanosilica layer 23 as a nanosilica particle size 9 nm.

Test conditions: the sliding speed was 12[ mm/s ], and the test pieces were used as the annular test pieces φ16X107.4X17 [ mm ] and the disk-shaped test pieces 20X 4[ mm ], and were loaded for 60 seconds under a vertical load of 50N, and then were stopped after waiting for 60 seconds under 4800N for 30 seconds every 200N load, from 200N to 4800N.

Comparative example 2

The annular test piece of comparative example 2 was prepared without the hard layer 12 (base material SUS 440C), and the nanosilica layer 13 was prepared with a nanosilica particle diameter of 9 nm. Similarly, the disk-shaped test piece of comparative example 2 was formed without the hard layer 22 (base material SUS 440C), and the nano silica layer 23 was formed with a nano silica particle size of 9 nm. The test conditions were the same as in example 2.

(test results of example 2 and comparative example 2)

Fig. 9 is a graph showing the results of the frictional wear test of example 2 and comparative example 2. That is, the data of "a-C: H" of example 2 and "SUS440C" of the Vickers hardness Hv653 (general value) of comparative example 2 in the hard layer carrying the nano-silica particles are shown in the graph of FIG. 9. In example 2 and comparative example 2, silicon was supported on both sliding surfaces (hard layers 12 and 22). In "a-C: H" of example 2, the surface contact pressure at the time of low friction sliding was at least 48.5MPa or more, but in the case of "SUS440C" of comparative example 2, low friction could not be exhibited. From the above, it is shown that the hardness of the hard layers 12, 22 is important for improvement of water-lubricated sliding.

Example 3

Example 3 is a test for confirming the effect of the second embodiment. The annular test piece (first sliding member 10) of example 3 was a DLC coating (a-C: H) having a Si content of 0% in the hard layer 12, and was made of nano silica without being supported. The disk-shaped test piece (second sliding member 20) of example 2 was obtained by forming the hard layer 22 as a DLC coating having a Si content of 25%, and forming the nano silica layer 23 as a nano silica particle size 9 nm.

(test results of example 3)

Fig. 10 is a graph showing the results of the frictional wear test of example 3. The ring-shaped test piece has a hard layer 12 of a-C: H and no silicon supported thereon, and the disk-shaped test piece has a hard layer 22 of Si-DLC25% and nano silica particles supported thereon at 9 nm. As shown in fig. 10, the surface-to-surface contact pressure during low friction sliding is at least 48.5 MPa. The results of example 3 show that even if silicon (hard layer 22) is supported on only one surface, low friction is exhibited.

Example 4

Example 4 is a test for the purpose of confirming the operational effects of the third embodiment. The annular test piece (first sliding member 10) of example 4 was a DLC coating (a-C: H) having a Si content of 0% in the hard layer 12, and was made of nano silica without being supported. The disk-shaped test piece (second sliding member 20) of example 4 was carried with a base material 21 (also referred to as a hard layer 22) of silicon nitride and a nanosilica layer 23 of nanosilica having a nanosilica particle diameter of 9 nm.

Example 5

Like example 4, example 5 is a test for the purpose of confirming the effect of the third embodiment. The annular test piece (first sliding member 10) of example 5 was a DLC coating (a-C: H) having a Si content of 0% in the hard layer 12, and was made of nano silica without being supported. The disk-shaped test piece (second sliding member 20) of example 5 was carried with a base material 21 (also referred to as a hard layer 22) of silicon carbide and a nanosilica layer 23 of nanosilica having a nanosilica particle diameter of 9 nm. The test conditions were the same as in example 4.

(test results of example 4 and example 5)

Fig. 11 is a graph showing the results of the frictional wear test of examples 4 and 5. Fig. 11 shows the friction test results of the ring-disk test in the case where the base material 21 is silicon nitride or silicon carbide. As shown in fig. 11, the surface-to-surface contact pressure during low friction sliding is at least 48.5 MPa. This means that the hard layer 22 does not necessarily need to be coated with a hard film such as DLC, and the base material 21 may also serve as the hard layer 22 as long as it has sufficient hardness.

Example 6

The annular test piece (first sliding member 10) of example 6 was obtained by using a DLC coating having a Si content of 25% as the hard layer 12, and using a nanosilica layer 13 having a nanosilica particle diameter of 9nm as the support. The disk-shaped test piece (second sliding member 20) of example 6 was obtained by forming the hard layer 22 as a DLC coating having a Si content of 25%, and forming the nano silica layer 23 as a nano silica particle size 9 nm.

Test conditions: the sliding speed was 100[ mm/s ], and the test pieces were respectively annular test pieces φ16×φ11.4× 7[ mm ] and disk-shaped test pieces 20×20×4[ mm ], and were loaded under a vertical load of 50N for 60 seconds, and then were stopped after waiting for 60 seconds at 4800N for 30 seconds every 200N load, from 200N to 4800N.

(test results of example 6)

Fig. 12 is a graph showing the results of the frictional wear test of example 6. Friction test results of the ring test in which the sliding speed was changed to 100[ mm/s ]. As shown in FIG. 12, the surface-to-surface contact pressure during low friction sliding is at least 48.5[ MPa ] or more. According to example 6, it was shown that even at a coasting speed of 100[ mm/s ], a low friction slip was maintained.

Example 7

Example 7 is a test for the purpose of confirming the operational effects of the fourth embodiment. The annular test piece (first sliding member 10) of example 7 had a structure in which the base material 11 was made of silicon carbide ceramic and the base material 11 itself also served as the hard layer 12, and the nanosilica layer 13 was supported by nanosilica having a particle diameter of 9 nm. The disk-shaped test piece (second slide member 20) of example 7 had a structure in which the base material 21 was made of silicon carbide ceramic and the base material 21 itself also served as the hard layer 22, similarly to the annular test piece, and the nanosilica layer 23 was supported with nanosilica particle diameter of 9 nm.

Test conditions: the sliding speed was 300[ mm/s ], and the friction coefficient was increased at 1080N at 30 seconds every 200N load from 200N after 60 seconds load using the ring-shaped test piece φ16X107.4X17 [ mm ] and the disk-shaped test piece 20X10X104 [ mm ] respectively, and the test was completed.

Comparative example 3

For comparison with example 7, the frictional wear test of comparative example 3 was performed under the same test conditions. The annular test piece (first sliding member 10) of comparative example 3 had a structure in which the base material 11 was made of silicon carbide ceramic and the base material 11 itself also served as the hard layer 12, and the nanosilica was made unsupported. The disk-shaped test piece (second slide member 20) of example 7 had a structure in which the base material 21 was made of silicon carbide ceramic and the base material 21 itself also served as the hard layer 22, similarly to the annular test piece, and the nano silica was made unsupported. After 60 seconds of loading at a vertical load of 50N, the friction coefficient increased at 400N at 30 seconds per 200N load from 200N, and the test ended.

(test results of example 7 and comparative example 3)

Fig. 13 is a graph showing the results of the frictional wear test of example 7 and comparative example 3. In the graph of fig. 13, the vertical axis represents the friction coefficient, and the horizontal axis represents the inter-surface contact pressure. As shown in fig. 13, in example 7, the surface-to-surface contact pressure at the time of sliding reached 10MPa under a step load, and 4MPa in comparative example 3. In addition, the minimum friction coefficient in example 7 was expressed as 0.001 or less below 0.01, and an ultra-low friction sliding state was achieved. In the present specification, the ultra-low friction sliding means sliding with a friction coefficient of 0.01 or less.

Example 8

Example 8 is a test for confirming that the ultra-low friction is stably maintained at a sliding distance of 1000m in example 7. The annular test piece (first sliding member 10) of example 8 had a structure in which the base material 11 was made of silicon carbide ceramic and the base material 11 itself also served as the hard layer 12, and the nanosilica layer 13 was supported by nanosilica having a particle diameter of 9 nm. The disk-shaped test piece (second slide member 20) of example 7 had a structure in which the base material 21 was made of silicon carbide ceramic and the base material 21 itself also served as the hard layer 22, similarly to the annular test piece, and the nanosilica layer 23 was supported with nanosilica particle diameter of 9 nm.

Test conditions: the sliding speed was 300[ mm/s ], and the sliding was performed at a constant load of 500N for 30 seconds per 100N load until the sliding distance reached 1000m by using test pieces of annular test pieces φ16X1.4X 7[ mm ] and disk-shaped test pieces 20X 4[ mm ] under a vertical load of 50N for 60 seconds, respectively.

(test results of example 8)

Fig. 14 is a graph showing the results of the frictional wear test of example 8, in which the left vertical axis shows the contact pressure between surfaces, the right vertical axis shows the coefficient of friction, and the horizontal axis shows the sliding distance. As shown in fig. 14, in example 8, the coefficient of friction was about 0.002, which was lower than 0.01, at the surface contact pressure of 5MPa until the sliding distance of 1000m, indicating that sliding was performed while maintaining ultra-low friction.

Example 9

The annular test piece (first sliding member 10) of example 9 was obtained by forming the hard layer 12 as a DLC coating having a Si content of 50%, and forming the nano silica layer 13 as a nano silica particle size 9 nm. The disk-shaped test piece (second sliding member 20) of example 8 was obtained by forming the hard layer 22 as a DLC coating having a Si content of 50%, and forming the nano silica layer 23 as a nano silica particle size 9 nm.

Test conditions: the sliding speed was 300[ mm/s ], and the friction coefficient was increased at 1200N at 30 seconds every 200N load from 200N after 60 seconds load using the ring-shaped test piece [ phi ] 16X phi 11.4X 7[ mm ] and the disk-shaped test piece [ 20X 4[ mm ] respectively, and the test was ended.

(test results of example 9)

Fig. 15 is a graph showing the results of the frictional wear test of example 9. As shown in FIG. 15, in example 9, the friction coefficient was significantly lower than 0.01 in the contact pressure between surfaces of 1 to 12[ MPa ]. This shows that ultra-low friction sliding with a friction coefficient lower than 0.01 is achieved.

< modification >

The present invention is not limited to the above-described embodiments and examples, and various modifications may be made without departing from the spirit of the present invention. For example, in the above embodiments, the first slide member 10 and the second slide member 20 are not limited to the configurations using the annular test piece and the disk-shaped test piece, respectively. For example, the first slide member 10 and the second slide member 20 may be configured by using a large-diameter cylindrical member and a small-diameter cylindrical member, and performing water lubrication sliding between the inner peripheral surface of the large-diameter cylindrical member and the outer peripheral surface of the small-diameter cylindrical member. Alternatively, as the first slide member 10 and the second slide member 20, a pair of flat or plate-like members having a flat sliding surface in common may be used, and water lubrication sliding may be performed between the flat sliding surfaces.

Industrial applicability

The present invention is applicable to a so-called slide structure having first and second slide members each having a slide surface, the slide surfaces being in contact with each other via a water layer, thereby sliding the first and second slide members relative to each other, and an apparatus including the same. For example, the present invention can be applied to various fields such as sealing portions of fluid machines such as piston rings and cylinders, sliding structures such as sliding bearings and mechanical seals of rotating shafts, and vehicles and machine tools using these sliding structures.

Description of the reference numerals

1 sliding Structure (first embodiment)

2 sliding Structure (second embodiment)

3 sliding Structure (third embodiment)

4 sliding Structure (fourth embodiment)

10 first slide member

11 base material

12 hard layer

13 nm silicon dioxide layer

20 second slide member

21 base material

22 hard layer

23 nm silicon dioxide layer

30 water layer

Claims

1. A sliding structure comprises first and second sliding members each having a sliding surface, wherein the sliding surfaces are in contact with each other via a water layer, and the first and second sliding members slide relative to each other,

the first and second sliding members each have a base material and a hard layer as the sliding surface on the surface of the base material, and

the hard layer of at least one of the first and second sliding members includes a nanosilica layer carrying nanosilica particles.

2. The sliding structure according to claim 1, wherein the hard layer of the at least one has hydroxyl groups at a surface.

3. The sliding structure according to claim 1, wherein the nanosilica layer is supported on the hard layer in association with covalent bonds between activated hydroxyl groups of the hard layer and hydroxyl groups of the nanosilica particles.

4. The sliding structure according to any one of claims 1 to 3, wherein each of the hard layers of both the first and second sliding members is provided with the nano silica layer.

5. The sliding structure according to any one of claims 1 to 3, wherein the hardness of each hard layer is 1000Hv or more.

6. The sliding structure according to claim 5, wherein the hard layer of at least one of the first and second sliding members is composed of diamond-like carbon formed on the surface of the base material.

7. The sliding structure according to claim 6, wherein the diamond-like carbon contains silicon.

8. The sliding structure according to any one of claims 1 to 3, wherein the hard layer of at least one of the first and second sliding members is a part of the base material.

9. The sliding structure according to claim 8, wherein the base material constituting the hard layer is composed of ceramic.

10. The sliding structure according to claim 8, wherein the hard layers of both the first and second sliding members are part of the base materials,

each of the base materials constituting each of the hard layers is made of ceramic.